Why you forget new words, and how to make them stick

You read a beautiful word, look it up, and a week later it is gone. Here is what memory research says about forgetting, and a simple way to keep the words you collect.

You come across a word you love, petrichor, the earthy smell of rain on dry ground. You look it up, you smile, and a week later you cannot remember it. This is not a lack of talent. It is how memory works, and it can be worked with.

The forgetting curve

In 1885 the German psychologist Hermann Ebbinghaus measured his own memory with lists of nonsense syllables. He found that we lose most of what we learn within the first days, quickly at first, then more slowly. Each time we review, the curve flattens: the memory lasts longer before it fades again.

The practical lesson is simple: one long session is not enough, a few short ones spread over time are.

Spaced repetition: review just before you forget

Spaced repetition puts that lesson to work. You review a word soon after learning it, then after a longer gap, then a longer one again: a day, three days, a week, a month. Each review comes just as the word was about to slip away, which is exactly when it strengthens memory the most.

In the 1970s the German science writer Sebastian Leitner turned this into a box of flashcards: cards you get right move to a box you review less often; cards you miss go back to the first box. Every spaced repetition app is a descendant of that box.

Recall beats rereading

Rereading a definition feels productive, but it mostly builds familiarity. Trying to recall the word, before you see the answer, is what makes it stay. Psychologists call it the testing effect. A quiz, a flashcard or a word game all force that small effort of retrieval, and that effort is the point.

Five habits that help

Keep the words you meet. A word from your own reading means more than one from a generic list.
Learn it with its story. Where it comes from, a real sentence, a picture: each link is one more way back to it.
Test yourself, don't just reread. Cover the definition and try first.
Review a little, often. Five minutes a day beats an hour once a week.
Use it. Write it in a message or say it out loud. A word you use is a word you keep.

Back to petrichor

Petrichor comes from Greek petra, stone, and ichor, the fluid said to run in the veins of the gods. Now you have the word, its meaning and its story. Review it tomorrow, and again next week, and it is yours.